# Python: Find the indices of two numbers that sum to 0 in a given list

## Python Programming Puzzles: Exercise-29 with Solution

Write a Python program to find the indices of two numbers that sum to 0 in a given list of numbers.

Input: [1, -4, 6, 7, 4] Output: [4, 1] Input: [1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20] Output: [1, 7]

**Pictorial Presentation:**

**Sample Solution-1:**

**Python Code:**

```
#License: https://bit.ly/3oLErEI
def test(nums):
s = set(nums)
for i in s:
if -i in s:
return [nums.index(i), nums.index(-i)]
nums = [1, -4, 6, 7, 4]
print("Original List:")
print(nums)
print("Indices of two numbers that sum to 0 in the said list:")
print(test(nums))
nums=[1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20]
print("\nOriginal List:")
print(nums)
print("Indices of two numbers that sum to 0 in the said list:")
print(test(nums))
```

Sample Output:

Original List: [1, -4, 6, 7, 4] Indices of two numbers that sum to 0 in the said list: [4, 1] Original List: [1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20] Indices of two numbers that sum to 0 in the said list: [1, 7]

**Flowchart:**

**Sample Solution-2:**

**Python Code:**

```
#License: https://bit.ly/3oLErEI
def test(nums):
result = []
# For each index in the list:
for ind in range(len(nums)):
# For each index in the list:
for i in range(len(nums)):
# If the number at the current index and the other index sum to zero
if ind != i and nums[ind] + nums[i] == 0:
result.append(ind)
result.append(i)
# Found the indices; no need to go through the whole list
return result
nums = [1, -4, 6, 7, 4]
print("Original List:")
print(nums)
print("Indices of two numbers that sum to 0 in the said list:")
print(test(nums))
nums=[1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20]
print("\nOriginal List:")
print(nums)
print("Indices of two numbers that sum to 0 in the said list:")
print(test(nums))
```

Sample Output:

Original List: [1, -4, 6, 7, 4] Indices of two numbers that sum to 0 in the said list: [1, 4] Original List: [1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20] Indices of two numbers that sum to 0 in the said list: [1, 7]

**Flowchart:**

**Python Code Editor :**

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